Spontaneous release of gastric pressure is often associated with reflux, which is the transport of stomach contents to the pharynx. Gastro-esophageal “reflux fluid” as used herein includes any gas, any liquid, any partially solid and liquid substance or any material that can be expelled from the stomach into the patient's pharynx. Fluids that commonly accumulate in the stomach of a tube-fed patient include the tube-feeding formula, swallowed saliva (more than about 0.8 L/day), gastric secretion (about 1.5 L/day), and regurgitated small bowel secretion (about 2.7 to 3.7 L/day) into the stomach. Gastro-esophageal reflux (GER) often appears as an intermittent more or less massive, bolus-like regurgitation of stomach contents, but also can manifest as a continuous, silent ascension and descension of liquid and solid material between the gastrointestinal tract and the pharyngeal tract. GER alongside of gastric feeding and decompression tubes in intubated patients, both ventilated and spontaneously breathing, is a common problem in ICU therapy, being associated with a high infection relevance.
Especially under so called intra-gastric or intra-duodenal feeding, the incidence of reflux of stomach contents into the pharynx of the patient is increased. Gastric, duodenal or enteral feeding is a form of hyper-alimentation and metabolic support in which nutrient formulas or medicaments are delivered directly to the gastrointestinal tract, either the stomach or the duodenum. In the majority of cases, nutrient administration is accomplished through use of a tube based device or system, delivering the nutrient through the patient's pharynx and esophagus directly into the stomach, the duodenum or small intestinum (jejunum), often referred to as so-called enteral feeding. Certain enteral feeding devices include pumps that deliver feeding fluid to the patient. Other enteral feeding devices rely upon gravity to move the feeding fluid from a container (suspended above patient level) to the patient.
Enteral tubes for providing food and medication to a patient have been used in medical settings for many years. Examples of enteral feeding devices are described in U.S. Pat. Nos. 4,666,433; 4,701,163; 4,798,592; and 4,685,901, which are hereby incorporated herein in their entireties for all purposes by this reference. In critical care therapy, gastric (enteral) feeding is usually performed via so called naso-gastric decompression catheters (NG-tubes), which are primarily used to release pressure building up in the stomach of a patient. Excessive gastric pressure may result from the accumulation of liquid intestinal secretions, feeding solution applied into the stomach or duodenum, abdominal motility, body movement or positioning of the patient, or through normal formation of gas. For decompression of gastric pressure and drainage of gastric contents, such patients may be intubated with so called naso-gastric or oro-gastric tubes or probes. An example of one such stomach probe is described in German Utility Model Application No. 202006002832.3. Another is described in U.S. Pat. No. 6,551,272 B2, which is hereby incorporated herein in its entirety for all purposes by this reference.
Because solids and/or higher viscosity liquid secretions frequently obstruct the drainage lumen of a stomach probe, in many cases stomach probes insufficiently decompress the stomach. The insufficient decompression of the stomach permits reflux of fluids through the esophageal lumen alongside the NG tube. Further, instead of preventing GER, the literature describes the trans-esophageal passage of the rigid decompression tube shaft as itself impairing the seal efficacy of the esophagus and its sphincters by partially opening the sphincters and thus facilitating the ascension of secretions from the stomach into the pharynx alongside the tube shaft. Studies have shown that while GER occurs in about 15% of supine positioned patients without NG tubes, the prevalence of GER in supine positioned patients with NG tubes may increase to about 80% of cases.
Moreover, GER occurs in critically ill patients even in the absence of nasogastric (NG) tubes and enteral delivery of feeding solutions. Up to 30% of patients who are kept in the supine position are estimated to have GER.
The free communication of secretions between pharynx and stomach often results in a state of continuous ascension and decension of high volumes of colonized fluids, which may be on the order of several hundred milliliters per day or even on the order of liters per day. Typically, after about 4 to 6 days of mechanical ventilation, a mixed bacterial flora becomes established and populates the upper GI-tract as well as the entity of the pharyngeal, i.e., cranio-facial cavities. Such colonized material may pool in predisposed spaces such as the maxillary or sphenoidal sinuses, representing a most relevant source for bacteria inducing so called ventilator-associated pneumonia (VAP) as well as an origin for the septic spread of bacterial pathogens.
The free communication between the pharyngeal and gastro-intestinal compartment also impairs gastric delivery of enteral feeding solutions, which frequently becomes a problem in administering sufficient calories in the natural way via the upper GI-tract, and may require expensive and complication associated par-enteral feeding. In many cases, one can observe that feeding solution runs out of the patient's oral and nasal openings, implying that the reflux volume has been high and that all cranio-facial surfaces have been covered with a layer of bacteria feeding nutrients, supporting a major reservoir of pathogenic bacteria, especially in the etiology of VAP.
Preventive strategies against reflux of gastro-esophageal contents were essentially medicinal/antibiotic based, as for example so-called selective digestive decontamination (SDD) of the pharynx and the stomach by application of topical, non-resorbable antibiotics. Additionally, oral care procedures are being performed on most ICU wards, whereby the oro-pharyngeal cavity is cleaned by a swab or a brush, applying a small volume of water or cleaning solution into the oro-pharynx. Further, medication has been administered to long term ventilated patients, preventing bacterial colonization of the stomach by keeping the stomach pH within an acidic, antiseptic range.
Perhaps the most frequently practiced and probably most efficient preventive measure against reflux of gastro-esophageal contents has been to elevate the patient's upper body into a semi-recumbent position, thereby reducing the ascension of colonized gastric material into the pharynx. At least two studies have shown a reduction of GER when critically ill patients are kept in the semi-recumbent position. Thus, patients undergoing mechanical ventilation are usually put in a supine or a semi-recumbent body position.
When gastrointestinal motility is normal, secretions and ingested fluids are propelled forward by the upper gastro-intestinal tract with little difficulty. Significant gastrointestinal dysmotility, ranging from moderate delay in gastric emptying to marked gastric paresis, has been described in patients with a variety of clinical conditions such as burns, sepsis, trauma, surgery, and shock. GER frequently can be observed during tracheal intubation and mechanical ventilation, where sphincter function and gastric motility may be impaired as a side effect of the analog-sedating medication applied, and an extended period of demobilization of the patient in supine position. In order to prevent reflux under gastric feeding, respectively to support gastric and duodenal motility and emptying, ICU clinicians administer special drugs like e.g. metoclopramid.
When the combination of feeding solution blended with gastro-intestinal fluid can freely communicate between the upper GI tract and the entity comprised of all the cranio-facial spaces connected to the patient's pharynx, the patient can suffer severe consequences in several regards:                First, feeding solution is lost, and necessary calories cannot be administered successfully, resulting in the need for costly prolonged par-enteral patient feeding.        Second, the mucosal surfaces of the cranio-facial cavities are getting covered intermittently with nutrients contained in the feeding solution, providing ideal growth conditions for bacteria, increasing the risk of colonization with bacteria relevant for the development ventilator associated pneumonia (VAP). Pharyngeal secretions, descending via the tracheal tube cuff to the distal airways are known to be a major cause of pulmonary infections in the intubated and ventilated patient.        Third, feeding solution, which is pooling in the remote cranio-facial cavities as the naso-pharynx and the para-nasal sinuses, cannot be removed by state of the art care techniques, may turn into a purulent state and become a permanent source for VAP pathogens or bacteria causing septic complications, by so called translocation of the bacteria through the inflamed mucosa from the purulent pool into the blood stream.        
The measurement of esophageal and gastric pressures with balloon-tipped catheters has been employed with great success over the past half century to delineate the physiology of the respiratory system. The determination of so called trans-diaphragmatic pressure, which is usually detected by sensing the pressure gradient between a balloon element disposed in the esophagus and a balloon element disposed in the stomach or intestine, has led to the development of according measuring probes and pressure sensing hardware, whereby the balloons are small in dimension and incapable of effecting an esophageal seal function. The related hardware is set for pressure detection exclusively and cannot actively regulate a seal pressure gradient.
In recent years there have been clinical attempts to effect an esophageal balloon seal against gastric material ascending from the stomach into the pharynx, using probe material designed for esophageal bleeding intervention (Sengstaken Blakemore tubes). Orozco et al. (details) were able to show a significant reduction of gastro-esophageal reflux. However, the structures of the esophageal wall react extremely sensitively to persistent pressure or organ wall distension. Thus, such conventional blocking techniques, in which the hull of a sealing bladder structure is placed under tension, are not, or only with limitations, desirable in the case of the esophagus. Due to the potential esophageal trauma risk, the application period of the stationary pressured balloon was limited to 8 hours.
A stomach probe such as described in German Utility Model Application No. 202006002832.3 has an esophageal bladder and enteral feeding tube that are integrated such that the feeding tube sits at or near the center of the bladder when used in a patient. The feeding tube has a thin-walled bladder associated with the feeding lumen. Around the feeding lumen is either one or a plurality of ferrules that are used to conduct air or other gas along the length of the bladder. A stomach probe of this type has a lumen that is located on the delivery cannula in the region of the inflatable bladder, which arrangement guarantees a rapid equalization of volume between sections or partial volumes of the inflatable bladder. The lumen is arranged so that a channel is formed between the lumen and the delivery cannula, which is connected to the interior of the inflatable bladder via a number of openings, and which is arranged on the lumen. The interior of the inflatable bladder is connected to means for producing pressure in the inflatable bladder via the channel formed between the delivery cannula and the lumen. The lumen is thereby kept open by stent-like devices or spacers between an outer and an inner wall of the probe or the delivery cannula of the stomach probe. However, a stomach probe of this type is therefore much more complicated to produce than conventional stomach probes without a lumen, for example.